Sand production in many oil and gas producing areas of the world is a serious problem which costs the industry several million dollars annually, either as a result of repairs or lost production. Recent trends towards higher production rates has resulted in high pressure differentials across formations and has increased the severity of sand control problems. If sand production is not arrested or controlled, sand entrained in produced fluids can severely erode production equipment and reduce well productivity.
Sand control techniques include use of mechanical devices to separate entrained sand at a subsurface location and thereby prevent solids from entering a producting well. These devices normally include a sand screen which serves to screen out sand or is used in conjunction with gravel pack completions. In either type of completion, the screen is provided with particularly sized openings to cause sand grains to bridge. In completions which employ a screen without an aggregate, the screen openings are sized in relation to formation particles to effect particle bridging. In gravel pack completions, screen openings are sized in relation to the aggregate used outside the screen; and the aggregate is sized in relation to formation sand. Size relationships of the aggregate and/or screen are normally determined by well-known techniques which are based upon sieve analysis data obtained from formation.
Recent studies have shown that the use of techniques based upon sieve analysis data frequently results in a screen having too large openings. Microscopic examinations of typical cores reveal that particle sizes classified by standard screen sieves are composed of clusters of loosely bound grains as well as individual grains. On a sieve analysis curve, the clusters are classified according to the cluster size instead of individual grain size. However, under producing conditions, individual grains break away from the cluster and migrate individually.
Therefore, what is needed is a method and apparatus to more effectively bridge sand on a screen to more efficiently remove sand from produced hydrocarbonaceous fluids.